Use "timber line" in a sentence

1. Three well equipped sites above the timber line provide air and deposition data all year round.

2. In this case, over-heating is even greater than it was found in the zone above timber line.

3. Subsiding rapidly in elevation, it becomes a knobbed and Bouldered land which includes timber-line and the thin forests of wind-twisted pines which contend with the granite for foothold.